Pharmaceuticals are required to maintain the quality thereof for a long time during distribution, storage and the like, and high chemical and physical stability is demanded for compounds as effective components. Thus, for the effective components of pharmaceuticals, crystals which are expected to have high stability compared to amorphous products are commonly employed.
In screening the crystals of effective components of pharmaceuticals, it is difficult to find optimal conditions to obtain the crystals, and also even when the crystals can be obtained, the existence of crystalline polymorphs is problematic in many cases. This is because each crystal form has a different molecular packing arrangement in spite of the same chemical structure in the molecular unit, so that there are differences in chemical and physical stabilities between the crystal forms.
If the crystal form of a compound employed as an effective component of pharmaceuticals is selected incorrectly, the decrease in purity, change in hydration degree, change in crystal form and the like occur due to the external environment during storage, and it is difficult to maintain the quality of the compound, thereby resulting in unexpected situations such as the reduction in pharmacological effects and the occurrence of side effect depending on the crystal forms. Therefore, in cases where the crystals of the compound as an effective component of pharmaceuticals are successfully obtained, it is necessary to evaluate the crystalline polymorphs of the compound strictly.
On the other hand, (S,E)-2-(2,6-dichlorobenzamido)-5-[4-(methyl-pyrimidin-2-ylamino)phenyl]pent-4-enoic acid represented by Formula (I) below has been known to exhibit therapeutic effects on inflammatory bowel disease, allergic dermatitis, multiple sclerosis and leukemia (WO 2006/068213, WO 2007/145282, WO 2007/148648 and WO 2007/148676):

However, since it is impossible to predict the existence of crystalline polymorphs or stable crystal form from the chemical structure of the compound and, further, there may be a compound which cannot form a crystal, it is necessary to study conditions of forming a crystal for each compound in various ways. Although excellent effectiveness as an effective component of pharmaceuticals is confirmed for (S,E)-2-(2,6-dichlorobenzamido)-5-[4-(methyl-pyrimidin-2-ylamino)phenyl]pent-4-enoic acid, the existence of crystalline polymorphs or even the possibility of crystal formation have not been known at present, and to obtain the optimal crystal form was an important task for developing the compound as a pharmaceutical product.
It could therefore be helpful to provide a crystal of (S,E)-2-(2,6-dichlorobenzamido)-5-[4-(methyl-pyrimidin-2-ylamino)phenyl]pent-4-enoic acid having excellent chemical and physical stability, and a medical use thereof.